RU2212021C1 - Electromagnetic velocity converter - Google Patents

Abstract

FIELD: measurement of flow rates of current-conductive liquids in head-free big-diameter pipe-lines under varying level of canal filling. SUBSTANCE: velocity converter has body made of electric insulation material, ferromagnetic bar core housed inside it and multichannel measurement facility capable of cyclic interrogation of all pairs of electrodes placed on body along its two generatrixes. Excitation coil comprises sections which number corresponds to number of electrode pairs. Each section is separated from adjacent section by ferromagnetic plate put perpendicular to axis of core. Measurement facility has supply channels of excitation coil, each channel is connected for equal time period simultaneously with connection of electrode pair of corresponding section. EFFECT: high sensitivity of measurement of velocity thanks to formation of magnetic field at moment when only one pair of electrodes is measurement zone. 2 dwg

Description

 The invention relates to instrumentation, in particular to the field of flow measurement by an electromagnetic method, and can be used to measure the flow rate of electrically conductive liquids in pressure and non-pressure (with a changing level of filling of the channel) pipelines and channels.

 Known electromagnetic speed converters for measuring the flow rate of electrically conductive liquids having an electromagnetic system consisting of a core core, an excitation coil and electrodes in contact with the measured liquid, and a measuring device [1].

 The disadvantage of such electromagnetic speed transducers is the low accuracy of flow measurement in pressure-free pipelines due to the low accuracy of measuring the filling level of the channel with the measured medium.

 This disadvantage is eliminated in the electromagnetic speed converter for pipelines of large diameters, which is the closest technical solution to the proposed invention [2].

 Such a speed transducer [2] has a pipeline channel, a core made extended along the vertical diameter of the pipeline channel, an excitation coil, the turns of which are distributed along the entire length of the core, electrodes located on two oppositely located external generators of the housing in the plane of the channel cross-section, and the electrodes on the housing are arranged in pairs along lines perpendicular to the axis of the housing, and a multi-channel measuring device. Each input channel of the measuring device is connected to its corresponding pair of electrodes. A multi-channel measuring device consists of a switching device, a power supply of the excitation coil and a microprocessor unit for processing information and controlling the switching device. The switching device provides alternate connection of pairs of electrodes to the microprocessor unit. Information processing is performed programmatically by a special algorithm with the ability to calculate fluid flow.

 The disadvantage of this electromagnetic speed transducer is the low metrological and operational characteristics when measuring fluid flow. A known speed converter [2] creates a magnetic field of excitation simultaneously in all zones of the measuring electrodes. However, at each moment of time, a signal is taken only from any one pair of electrodes sequentially and alternately “interrogated” using a switching device. Moreover, at each moment, a signal is measured that arises only from an insignificant part of the total working magnetic field, i.e. only from a magnetic field formed in the local region of the liquid in the zone of one pair of electrodes being surveyed at the moment. The rest of the magnetic field created in the channel, including above the level of filling with the measured medium, is not used in this measurement period. Consequently, energy for its creation is spent unproductive.

 This disadvantage is eliminated in the proposed electromagnetic speed transducer: a magnetic field is created each time only in that local area in which a speed measurement is being performed at the same time, while there is no magnetic field in the zones of the remaining pairs of electrodes. This makes it possible, with the same energy expended in creating a magnetic field, to provide a significantly higher sensitivity for measuring speed and, therefore, to increase the accuracy of the measurement.

 The electromagnetic speed converter according to the invention comprises a housing made of an insulating material, inside the housing there is a ferromagnetic core core and an excitation coil, the turns of which are distributed along the entire length of the core; electrodes located on the housing in pairs along lines perpendicular to the axis of the housing, and a multi-channel measuring device with the number of inputs not less than the number of pairs of electrodes and the power supply of the excitation coil. The excitation coil consists of sections, which may be the same or different. The number of sections corresponds to the number of pairs of electrodes, each section being separated from the adjacent section by a plate made of ferromagnetic material located perpendicular to the axis of the core and the end surfaces tightly adjacent to the core and the inner surface of the housing, and the line connecting the pair of electrodes of this section is in the central plane cross section of each section. A multichannel measuring device has power channels for sections of the field coil, a corresponding section of the field coil is connected to each channel, and the power channel of the section is connected programmatically at the same time for the same time with the pair of electrodes of this section connected to the measuring channel. In other words, the power source of the field coil through the switching device is connected each time only to that section, the pair of electrodes of which is currently “interrogated”, i.e. connected to a measuring device. The role of ferromagnetic plates is to concentrate the magnetic field formed by the excitation coil of this section in the area of its pair of electrodes.

 The invention is illustrated in figures 1 and 2.

 In FIG. 1 shows a design diagram of an electromagnetic speed transducer.

 The speed converter comprises a housing 1 made of an insulating material, a ferromagnetic core 2, sections of the excitation coil 3, electrodes 4 and ferromagnetic plates 5. A switching device 6 connected to the electrodes and excitation coils is controlled by a microprocessor unit 7.

 Figure 2 shows the distribution of the magnetic field created by the excitation coil section.

 Each pair of electrodes and corresponding to this pair (i.e. this section) the excitation coil is connected to the inputs of the corresponding channel of the switching device 6.

 An electromagnetic speed transducer is mounted on a horizontal pipeline so that the axis of the speed transducer is parallel to the direction of gravity, and the plane in which the electrodes are located is perpendicular to the direction of flow of the measured fluid.

 Electromagnetic speed Converter operates as follows.

 Consistently, alternately and cyclically, a current is supplied to each of the sections of the excitation coil through a switching device, at which a magnetic field arises, which, due to the ferromagnetic plates located at the ends of the coil section, is concentrated in the measured medium only in the area near the electrodes of this section. Moreover, in the zones of the remaining pairs of electrodes there is no magnetic field. When a fluid moves through a channel in a fluid that intersects the magnetic field of the measuring electrodes in this section, an electric field is excited, the intensity of which, according to the law of electromagnetic induction, is proportional to the product of the magnetic field and the local flow velocity. The signal from this pair of electrodes enters the microprocessor unit.

 After the completion of each complete cycle of the survey of all pairs of electrodes, the volumetric flow rate of the liquid is calculated using the corresponding algorithm according to the results of measuring signals from all pairs of electrodes.

 The proposed electromagnetic speed transducer can be used for measuring the flow rate of electrically conductive liquids in closed and open channels.

SOURCES OF INFORMATION
1. US patent 4122714, G 01 F 1/58, 10/31/1978, Magnetic current meter for open channel flow measurement.

 2. Patent of Russia 2146041, G 01 F 1/58, 02/27/2000, Electromagnetic flowmeter.

Claims (1)

 An electromagnetic speed transducer comprising a housing of electrical insulating material, a ferromagnetic core, an excitation coil, the turns of which are distributed along the entire length of the core, electrodes arranged in pairs on the housing along its two generators, and a multi-channel measuring device configured to cycle through all pairs of electrodes by sequential switching measuring channels, characterized in that the excitation coil consists of sections, the number of which is equal to the number of pairs of electrodes, each section is separated from the adjacent section by a plate of ferromagnetic material located perpendicular to the axis of the core and the end surfaces adjacent to the core and the inner surface of the housing, and the measuring device has power channels for each section of the excitation coil and is configured to connect the channel power section at the same time time interval with connecting a pair of electrodes of this section to the measuring channel.

Images